Probabilistic risk assessment method development for high temperature gas-cooled reactors, 4; Use of operational and maintenance experiences with the high temperature engineering test reactor

Shimizu, Atsushi ; Sato, Hiroyuki  ; Nakagawa, Shigeaki  ; Ohashi, Hirofumi 

Present paper provides an approach to update PRA parameters using the operational and maintenance experience obtained from the HTTR. Firstly, components subject to investigation are selected with the following criteria; The component has safety function in commercial HTGR, the component is utilized in high temperature-irradiated condition, structure or mechanism of the action for the component is unique, and the component is installed in the HTTR. Secondly, component boundaries are clarified and raw data is collected from maintenance records, monthly surveillance test records, operation and maintenance database, etc. As a preliminary study, selected PRA parameters are updated using Bayesian methods to confirm the effectiveness of the use of the HTTR experience. The results showed that the use of HTTR operational and maintenance data is effective for HTGR reliability database development.